Process of obtaining calcium sulfate and by-products.



No. 712,225.. 4 Patented Dot-28,1902. H. n. wme.

PROCESS O F'OB TAINING CALCIUM SULFATE; 'AND BY-PBOOUGTS.

(A limion ua se'pc. 9. 1901. (No Model.)

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UNITED STATES ATENT I OFFICE. I

HERBERT H. WING, OF NEW BRIGHTON, NEW YORK.

PROCESS OF OBTAINING CALCIUM SULFATE AND BY-PRODUCTS.

SPECIFICATION forming part of Letters Patent No. 712,225, dated October 28, 1902. Application filed September 9, 1901 Serial No. '74:,717- (N specimens.)

. To all whom it may concern:

Be it known that I, HERBERT H. WING, a citizen of the United States, residing at New Brighton, in the county of Richmond and State of New York, have invented certain new and useful Improvements in Processes of Ohtaining Calcium Sulfate and By-Products; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The object of my invention is to utilize sulfur fumes in the production of chemical products in the place of other and more expensive chemicals which have hitherto always been used in the commercial production of such products, and also to use sulfur fumes, which are too dilute for any other known purpose; also, to produce by-products from a part or the Whole of the main products resulting from the absorption of the sulfur fumes or obtained as by-products in the production of still other main products from various other sources. By my process l am able to use sulfur fumes, which are contaminated with air or with air and carbonic-acid gas or with sulfuric-acid gas, besidesbeing able to use sulfur fumes, which are a waste product and often a great nuisance, so that in many cases they have to be got rid of at great expense. The chemical products which I produce from such fumes are at present produced by expensive chemicals, such as sulfuric acid or sodium sulfate and calcium chlorid, carbonate of magnesia, and sulfuric acid, 850. I am also able to produce valuable by-products from the main product obtained by the absorption of sulfur fumes, which product is also produced as aby-productin other chemical processes, so that my process can be applied on a muehlarger scale Without glutting the market with one product. Not only this, but the by-products have a much more extensive application and at the present time command higher prices than the so-called main product.

My process, in general terms, consists in first producing a mixture of the sulfite and sulfate of magnesium by bringing sulfur fumes and air into contact in the presence of moisture with magnesia, magnesium hydrate,

The pro- I the amount of oxidizing that the sulfite undergoes from the amount of air brought into contact with it and also on the amount of sulfuric acid contained in the fumes and pro duced in the passage of the gases through the apparatus. The temperature also influences the result, the higher temperature increasing the amount of sulfate produced. By continuing to pass the fumes through the solution of the sulfates and at the same time add: ing fresh quantities of magnesium compounds the oxidizing of the sulfite formed (which being insoluble remains suspended in the solution) is increased, and these conditions for obtaining the sulfate can be regulated so that all or substantially all of the sulfite is converted into sulfate. In this case the solution is allowed to stand and the insoluble impurities settled out or the solution filtered, and the pure sulfate of magnesium is obtained by crystallization. Instead of completing the oxidation of all of the sulfite directly in the liquor, the sulfite can be settled or filtered out and slightly heated in a drier or reverberatory furnace and exposed to an oxidizing atmosphere, when it will be-Very rapidly converted into sulfate. duced is then added to water and dissolved, the impurities settled or filtered out, and the pure sulfate crystallized and recovered.

Instead of having the sulfate of magnesium the product of the utilization of the sulfur fumes, as above described, or, instead of having it the by-product in the process of making liquefied carbonic-acid gas by treating magnesite with sulfuric acid, or, instead of having magnesium sulfate as the final product by solution and crystallization of Keiserite or other Stassfurt products, the production of magnesium sulfate can he largelyincreased over the present output by the method which I will describe, as the amount of sulfur fumes available is very great and the production of magnesium sulfate from the other two sources could belargely increased, provided a market could be found. for such magnesium sulfate. For this purpose I make use of sulfate of mag- The sulfate thus pro- I sulfate is brought into contact with a solution of calcium chlorid, whereby there is produced calcium sulfate and magnesium chlorid according-to the reaction.

The calcium sulfate being practically insoluble is precipitated, filtered, washed, and preferably dried, in which condition it is commercially known as crown-filler or pearl hardening. To the solution of magnesium chlorid I add calcium hydrate or lime or milk of lim'e,whereby there is produced magnesium hydrate and calcium chlorid. The magnesium hydrate being'insoluble is precipitated, and the liquor containing the calcium chlorid is then decanted. The magnesium hydrate thus produced can be used over again in the first step of the process, and the regenerated calcium chlorid can also be used over again in the third step of this process.

Instead of using lime containing only the oxidof calcium, as above mentioned, Ican use lime obtained from dolomite, and therefore containing both calcium and magnesium oxids. hen this kind of lime is used, more will be required, as only the calcium hydrate of the same acts on the magnesium chlorid; but the magnesium oxid in it will be converted into magnesium hydrate and Will'be obtained as such along with the magnesium hydrate from the magnesium chlorid, so that as much extra magnesium hydrate will be obtained as a by-product as is contained in the dolomite lime. Wherever lime or dolomite lime is to be used, it may be used either in the form of lime or as milk of lime, as may be preferred, the milk of lime being in all respects equivalent to the lime in the reactions herein described. As the magnesium hydrate which is thus obtained is more valuable than calcined magnesia or magnesite at certain 10- calities, the latter forms of magnesia may be used instead of the former for the first step of this process.

To carry out my process by utilizing sulfur fumes, a variety of diflerent forms of apparatus may be used. In the annexed drawings I have shown a form of apparatus which is adapted for such work.

Figure 1 represents in elevation, partly in section, the apparatus for carrying out the reactions hereinafter described. Fig. 2 represents in sectional elevation apparatus suitable for oxidizing the sulfite to sulfate.

In the drawings, X represents a source from which fumes containing sulfur dioXid may be obtained and may be a smelting-furnace, ore-roaster, or any apparatus from which fumes containing sulfur dioxid can be obtained.

A represents a dust collecting chamber for settling out any dust carried by the fumes.

TTrepresentpipes which convey the fumes to the absorbing apparatus L, which consists of a tank provided with means, as E E, for

agitating the contents, and mechanism, as G, for operating the agitators E E.

H represents a receiving-tank, preferably mounted on trunnions and in which is provided a perforated false bottom h and filtering materials W. This tank is connected by suitable flexible connections h to a pump I, whereby the liquid contents of tank H may be drained away from the solid matter, leaving the latter semidry.

M represents a trough or conveyer into which the drained contents of tank I-I may be emptied, as by tipping the same on its trun' nions, and by which conveyer the contents of tank II may be conducted to any other desired apparatus-as, for instance, to a drier or furnace N, as shown in Fig. 2.

0 represents a tank for crystallizing the magnesium sulfate, and P a tank for preparing milk of magnesia or any compound of magnesium which in the presence of moisture is decomposable by sulfur dioxid.

R represents a pump for forcing the magnesium emulsion from tank P into the absorbing apparatus L.

S is a pipe connecting the pump-R with the absorbing apparatus L.

D and C are tanks for treating the magnesium sulfate and magnesium chlorid.

F is a pump, and K and J are inlet and outlet pipes to said pump, by means of which the liquid contents of tanks 0 and D maybe transferred from one to the other or to the tank P.

The method of operating the apparatus shown in the drawings consists in first passing the sulfur fumes containing SO with some air and more or less SO from the source X through the dust-settling chamber A, then through the pipes T T and the absorbing apparatus L, through which they are drawn by pipe it by means of the suction maintained by the suction-blower U. The absorbing apparatus L is nearly filled with an emulsion of magnesium hydrate or any compound of magnesium which in the presence of moisture is decomposable by sulfur dioXid, which emulsion is prepared in the tank P and delivered to the absorber L by the pump R through the pipe S. The emulsion is kept agitated by means of the agitators E E and mechanism G, which is continuously operated. By passing the sulfur fumes containing air into the emulsion of magnesium hydrate or any other compound of magnesium which in the presence of moisture is decomposable by sulfur dioxid the monosulfite and sulfate of magnesium are produced, the proportion of sulfate increasing according to the amount of $0,, the amount of air in the fumes, the length of time the fumes are brought into contact with the magnesia compound,and the temperature of the same until in time all the monosulfite can be oxidized to sulfate, as before stated. Instead of oxidizing all the monosulfite first produced in the liquor, however, the passage of the fumes is preferably continued only uninto sulfate.

til all the magnesia contained in the liquor is neutralized and converted into monosulfite and sulfate, which can be ascertained by continuously testing the liquor foracid or alkaline reaction. The valve Z in the dischargepipe of tank L is then opened and the contents of the absorber are discharged into the filter-tank H. The monosulfite of magnesium is a whitish granular mud, from which most of the water is drained by drawing it through the filter and perforated bottom of the tank H by the pump I, leaving a semidry mass in the tank. The monosulfite of magnesium is removed from the tank, as by dumping it into the conveyer M, and is exposed to heat in a drier or furnace N in an oxidizing atmosphere, whereby the monosulfite is converted The solution passing through the filter H is forced by the pump I through the pipe 4) into the tank 0, where it is allowed to remain and the magnesium sulfate in solution is crystallized out. The sulfate produced in the drier or furnace N is placed in the tank H and sufficient hot water is added to it to dissolve the sulfate, producing a concentrated-solution. Then the pump I is started and the clear solution of magnesium sulfate is pumped into the tank 0 and allowed to crystallize with the first portion of magnesiu m sulfate. The insoluble impurities in the solution are left on the filter in H and are then removed. The mother-liquors left from crystallizing the magnesium sulfate can be used to make up the emulsions in the tank P until they are used so often as to contain too great an amount of impurities,when fresh water is used in place of the impure mother-liquors, which are thrown away. i

The crystallized magnesium sulfate obtained by the above method or as a by-product or main product in other chemical operations is then added to a solution of calcium chlorid contained in the tank D, whereby calcium sulfate (OaSO ,2H O) and a solution of magnesium chlorid (MgCl are produced, as be fore described. The insoluble calcium sulfate'is separated from the solution, washed, and preferably dried, in which condition it is in demand in the market and is known as crown-filler or pearl hardening. The solution of magnesium chlorid which is produced as above stated is forced by'the pump F into the tank 0. Into this solution lime,

or as an equivalent milk of lime, is added,

whereby calcium chlorid is regenerated (which can be used over again) and magnesium hydrate is produced, which being insolu.

ble is precipitated. The calcium-chlorid so-' lution is then pumped back intothe tank D, and the fiocculent magnesium hydrate precipitated is then pumped to the tank 1?, from which it is forced into the absorber L to be used over again, or it may bewashed and dried or made into carbonate and dried or used to make any of the marketable forms in which Instead of using the lime containing only calcium oxid in the tank O oxidizing conditions,

dolomite lime or milk of lime fromthe samecan be used, which, as before mentioned, requires more lime, but the magnesium which it contains forms the hydrate when slaked and increases the total amount of magnesium hydrate precipitated in the tank.

Whenever the sulfur fumes are mentioned as containing sulfur dioxid and air, .I do not desire to be understood as meaning to exclude the presence of the sulfur trioxid, which will vary according to the source from which. the fumes are obtained, and which, as before mentioned, can be a constituent of the fumes which I useoin this process. The designation of the mixture of sulfur dioxidand air is mentioned because without air being present the sulfite could not be converted into sulfate in the subsequent steps. In the claims I employ the term lime as a genericterm, including both ordinary lime and dolomite lime, and include also in that term milk of lime as an'equivalent for the lime itself.

, What I claim isl l. The herein-described process of obtaining calcium sulfate and a by-product which consists. in subjecting any compound of magnesium decomposable by sulfur dioxid inthe presence of moisture to the action of sulfur fumes containing sulfur dioxid and air in the presence of moisture, whereby the sulfite and sulfate of magnesium are produced; then exposing such mixture of sulfite and sulfate to fate to a solution of calcium chlorid whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it'was produced; then adding lime to the magnesium chlorid which remains .in solution in said liquor, whereby calcium chlorid and the byproduct magnesium hydrate are produced.

2. The herein-described process of obtaining calcium sulfate and a by-product which consists in subjecting any compound ofmagnesium decomposable by sulfur dioxid in the presence of moisture to the action of sulfur fumes containing sulfur dioxid and air in the presence of moisture, whereby the sulfite and whereby the sulfite is convertedinto sulfate; then adding the sul- ICO sulfate of'magnesium are produced; then exposing such mixture .of sulfite and sulfate to oxidizing conditions, whereby the. sulfite is converted into sulfate; then adding the sulfate to a solution of calciumchlorid whereby magnesium chlorid and calcium sulfate are produced; thenseparating the insoluble calcium sulfate from the liquorin which it was prod need; then addinglime to the magnesium ing calcium sulfate and a by-product which consists insubjecting anycompound of mag nesium decomposable by sulfur dioxid in the presence of moisture to the action of sulfur fumes containing sulfur dioxid and air in the presence of moisture, whereby the sulfite and sulfate of magnesium are produced; then exposing such mixture of sulfite and sulfate to oxidizing conditions whereby the sulfite is converted into sulfate; then adding the sulfate to a solution of calcium chlorid whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it was produced; then adding dolomite lime to the magnesium chlorid which remains in solution in said liquor whereby calcium chlorid and the by-product magnesium hydrate are produced.

4. The herein-described process of obtaining calcium sulfate and a by-product which consists in subjecting any compound of magnesium decomposable by sulfur dioxid in the presence of moisture to the action of sulfur fumes containing sulfur dioxid and air in the presence of moisture, whereby the sulfite and sulfate of magnesium are produced; then exposing such mixture of sulfite and sulfate to oxidizing conditions whereby the sulfite is converted into sulfate; then adding the sulfate to asolution of calcium chlorid whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it was produced; then adding dolomite lime to the magnesium chlorid which remains in solution in said liquor, whereby calcium chlorid and the by-product magnesium hydrate are produced; then separating the magnesium hydrate from the liquor in which the calcium chlorid remains in solution.

5. The herein-described process of obtaining calcium sulfate and a by-product which consists in subjecting any compound of magnesium decomposable by sulfur dioxid in the presence of moisture to the action of sulfur fumes containing sulfurdioxid and air in the presence of-moisture, whereby the sulfite and sulfate of magnesium are produced; then continuing the action of said fumes until all the sulfite of the mixture is converted into sulfate; then adding the sulfate to a solution of calcium chlorid, whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it was produced; then adding lime to the magnesium chlorid which remains in solution in said liquor, whereby calcium chlorid and the by-product magnesium hydrate are produced.

6. The herein-described process of obtaining calcium sulfate and a by-product which consists in subjecting any compound of magnesium decomposable by sulfur dioxid in the presence of moisture to the action of sulfur fumes containing sulfur dioxid and air in the presence of moisture, whereby the sulfite and sulfate of magnesium are produced; then continuing the action of said fumes until all the sulfite of the mixture is converted into sulfate; then adding the sulfate to a solution of calcium chlorid, whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it was produced; then adding lime to the magnesium chlorid which remains in solution in said liquor; whereby calcium chlorid and the by-product magnesium hydrate are produced; then separating the magnesium hydrate from the liquor in which the calcium chlorid remains in solution.

7. The herein-described process of obtaining calcium sulfate and a by-product which consists in subjecting any compound of magnesium decomposable by sulfur dioxid in the presence of moisture to the action of sulfur fumes containing sulfur dioxid and air in the presence of moisture, whereby the sulfite and sulfate of magnesium are produced; then continuing the action of said fumes until all the sulfite of the mixture is converted into sulfate; then adding the sulfate to a solution of calcium chlorid whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it was produced; then adding dolomite lime to the magnesium chlorid which remains in solution in said liquor, whereby calcium chlorid and the by-product magnesium hydrate are produced.

8. The herein-described process of obtaining calcium sulfate and a byproduct which consists in subjecting any compound of magnesium decomposable by sulfur dioxid in the presence of moisture to the action of sulfur fumes containing sulfur dioxid and air in the presence of moisture, whereby the sulfite and sulfate of magnesium are produced; then continuing the action of said fumes until all the sulfite of the mixture is converted into sulfate; then adding the sulfate to a solution of calcium chlorid whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it was produced; then adding dolomite lime to the magnesium chlorid which remains in solution in said liquor, whereby calcium chlorid and the by-product magnesium hydrate are produced; then separating the magnesium hydrate from the liquor in which the calcium chlorid remains in solution.

9. The herein-described process of obtaining calcium sulfate and a by-product which consists in subjecting any compound of magnesium decomposable by sulfur dioxid in the presence of moisture to the action of sulfur fumes containing sulfur dioxid and airin the presence of moisture, whereby the sulfite and sulfate of magnesium are produced; then separating the soluble sulfate in water from the insoluble sulfite; then exposing the sulfite to oxidizing conditions, whereby the sulfite is converted into sulfate; then adding the sulfate to a solution of calcium chlorid, whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it was produced; then adding dolomite lime to the magnesium chlorid which remains in solution in said liquor, whereby calcium chlorid and the by-product magnesium hydrate are produced.

10. The herein-described process of obtaining calcium sulfate and a by-product which consists in subjecting any compound of magnesium decomposable by sulfur dioxid in the presence of moisture to the action of sulfur fumes containing sulfur dioxid and air in the presence of moisture, whereby the sulfite and sulfate of magnesium are produced; then separating the soluble sulfate in water from the insoluble sulfite; then exposing the sulfite to oxidizing conditions, whereby the sulfite is converted into sulfate; then adding the sulfate to a solution of calcium chlorid, whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it was produced; then adding dolomite lime to the magnesium chlorid which remains in solution in said liquor, whereby calcium chlorid and the by-product magnesium hydrate are produced; then separating the magnesium hydrate from the liquor in which the calcium chlorid remains in solution.

11. The herein-described process of obtaining calcium sulfate and a by-product which consists in adding magnesium sulfate to a solution of calcium chlorid, whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sufate from the liquor in which it was produced; then adding lime to the magnesium chlorid which remains in solution in said liquor, whereby calcium chlorid and the by-product magnesium hydrate are produced.

12. The herein-described process of obtaining calcium sulfate and a by-product which consists in adding magnesium sulfate to a solution of calcium chlorid ,whereby magnesium chlorid and calcium sulfate are produced; then separating the insoluble calcium sulfate from the liquor in which it was produced; then adding lime to the magnesium chlorid which remains in solution in said liquor, whereby calcium chlorid and the by-product magnesium hydrate areproduced; then separating the magnesium hydrate from the liquor in which the calcium chlorid remains in solution.

13. The herein-described process of obtaining calcium sulfate and a by-product which consists in adding magnesium sulfate to a solution of calcium chlorid,whereby' magnesium chlorid and calcium sulfate are produced, then separating the insoluble calcium sulfate from the liquor in which it was produced,

then adding dolomite lime to the magnesium chlorid which remainsin solution in said liquor, whereby calcium chlorid and the byproduct magnesium hydrate are produced.

14. The herein-described process of obtaining calcium sulfate and a by-product which consists in adding magnesium sulfate to a solution of calcium chlorid,whereby magnesium chlorid and calcium sulfate are produced,

then separating the insoluble calcium sulfate from the liquor in which it was produced, then adding dolomite lime to the magnesium chlorid which remains in solution in said liquor, whereby calcium chlorid and the byproduct magnesium hydrate are produced; then separating the magnesium hydrate from the liquor in which the calcium chlorid remains in solution.

In testimony whereof 1 hereto aflix my signature in presence of two witnesses.

HERBERT H. WING.

Witnesses:

O. H. INGALLS, T. H. SPRAT. 

